1. Field of the Invention
The present invention relates to a shifting mechanism for a gear change transmission and more specifically to a shifting mechanism for a gear change transmission where the shift forks are initially moved and/or preloaded by a plurality of springs displaced by a linear actuator.
2. Description of the Prior Art
Gear change transmissions utilizing shift bar housing assemblies wherein one or more axially moveable shift bars, also known as shift rails or shift rods, each carrying or associated with a shift fork, are selectively axially moved to engage or disengage a selected transmission gear. The movement of the shift bar causes an axial movement of a clutch member, or of a gear carrying clutch teeth or of a jaw clutch, as are well known in the prior art, and may be seen by reference to U.S. Pat. Nos. 4,445,393; 4,754,665; 4,876,924; and 5,053,961, the disclosures of which are hereby incorporated by reference.
Non-operator actuated shift bar housing assemblies which are usually actuated by pressurized hydraulic fluid, pressurized air, or electric motors and the controls therefor, are also well known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,428,248; 4,445,393; 4,722,237 and 4,873,881, all assigned to the assignee of this invention and all hereby incorporated by reference.
While the prior art actuated shift bar housing assemblies are generally satisfactory and are presently utilized or under development for remotely controlled and/or automatically controlled change gear transmissions, the prior art assemblies are not totally satisfactory as they are complicated and/or expensive to produce, install and/or service. These prior art systems are also slow and difficult to control due to the compressibility of the fluid used to power the shift rails or the high current experienced by the electric actuators when a gear change cannot be immediately effectuated due to non-synchronization or torque loading in the gear box.